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[1.7.x] Fixed is_safe_url() to handle leading whitespace.

This is a security fix. Disclosure following shortly.
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timgraham committed Dec 3, 2014
1 parent 41b4bc7 commit de67dedc771ad2edec15c1d00c083a1a084e1e89
Showing with 45 additions and 1 deletion.
  1. +1 −0 django/utils/http.py
  2. +14 −0 docs/releases/1.4.18.txt
  3. +14 −0 docs/releases/1.6.10.txt
  4. +14 −0 docs/releases/1.7.3.txt
  5. +2 −1 tests/utils_tests/test_http.py
@@ -272,6 +272,7 @@ def is_safe_url(url, host=None):
"""
if not url:
return False
url = url.strip()
# Chrome treats \ completely as /
url = url.replace('\\', '/')
# Chrome considers any URL with more than two slashes to be absolute, but
@@ -31,6 +31,20 @@ development server now does the same. Django's development server is not
recommended for production use, but matching the behavior of common production
servers reduces the surface area for behavior changes during deployment.

Mitigated possible XSS attack via user-supplied redirect URLs
=============================================================

Django relies on user input in some cases (e.g.
:func:`django.contrib.auth.views.login` and :doc:`i18n </topics/i18n/index>`)
to redirect the user to an "on success" URL. The security checks for these
redirects (namely ``django.util.http.is_safe_url()``) didn't strip leading
whitespace on the tested URL and as such considered URLs like
``\njavascript:...`` safe. If a developer relied on ``is_safe_url()`` to
provide safe redirect targets and put such a URL into a link, they could suffer
from a XSS attack. This bug doesn't affect Django currently, since we only put
this URL into the ``Location`` response header and browsers seem to ignore
JavaScript there.

Bugfixes
========

@@ -29,3 +29,17 @@ containing underscores from incoming requests by default. Django's built-in
development server now does the same. Django's development server is not
recommended for production use, but matching the behavior of common production
servers reduces the surface area for behavior changes during deployment.

Mitigated possible XSS attack via user-supplied redirect URLs
=============================================================

Django relies on user input in some cases (e.g.
:func:`django.contrib.auth.views.login` and :doc:`i18n </topics/i18n/index>`)
to redirect the user to an "on success" URL. The security checks for these
redirects (namely ``django.util.http.is_safe_url()``) didn't strip leading
whitespace on the tested URL and as such considered URLs like
``\njavascript:...`` safe. If a developer relied on ``is_safe_url()`` to
provide safe redirect targets and put such a URL into a link, they could suffer
from a XSS attack. This bug doesn't affect Django currently, since we only put
this URL into the ``Location`` response header and browsers seem to ignore
JavaScript there.
@@ -30,6 +30,20 @@ development server now does the same. Django's development server is not
recommended for production use, but matching the behavior of common production
servers reduces the surface area for behavior changes during deployment.

Mitigated possible XSS attack via user-supplied redirect URLs
=============================================================

Django relies on user input in some cases (e.g.
:func:`django.contrib.auth.views.login` and :doc:`i18n </topics/i18n/index>`)
to redirect the user to an "on success" URL. The security checks for these
redirects (namely ``django.util.http.is_safe_url()``) didn't strip leading
whitespace on the tested URL and as such considered URLs like
``\njavascript:...`` safe. If a developer relied on ``is_safe_url()`` to
provide safe redirect targets and put such a URL into a link, they could suffer
from a XSS attack. This bug doesn't affect Django currently, since we only put
this URL into the ``Location`` response header and browsers seem to ignore
JavaScript there.

Bugfixes
========

@@ -107,7 +107,8 @@ def test_is_safe_url(self):
'http:/\//example.com',
'http:\/example.com',
'http:/\example.com',
'javascript:alert("XSS")'):
'javascript:alert("XSS")',
'\njavascript:alert(x)'):
self.assertFalse(http.is_safe_url(bad_url, host='testserver'), "%s should be blocked" % bad_url)
for good_url in ('/view/?param=http://example.com',
'/view/?param=https://example.com',

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